1. Field of the Invention
The invention relates an antenna device for a communication terminal, e.g. hand-portable phone.
2. Description of Prior Art
During the past years use of internal antennas for cellular terminals has become more and more popular among the users. Today approximately 50% of the manufactured phones are equipped with internal antennas.
According to a first aspect of the invention there is provided an antenna device comprising two substantial planar and conductive elements where the first element is acting as radiator of the antenna, and the second element is acting as ground plane for the radiator of the antenna, said two conductive elements are mounted substantial in parallel by means of a non-conductive housing, and said radiator of the antenna is facing towards the ground plane of the antenna with the cavity in between the first and second conductive elements being filled with air. Hereby there is provided a structure that reduces the dielectric loss in the antenna. This increases the efficiency of the antenna.
According to a second aspect of the invention there is provided an antenna device comprising radiator elements integrated into a single radiator plate of a patch antenna being operable in at least two frequency bands said antenna comprises adjustment parts for individually adjusting said at least two bands by adjusting the size of these adjustment parts during manufacturing. Hereby the two bands of the antenna are designed so independent tuning of GSM frequencies and PCN frequencies is obtained. GSM is tuned by changing the length of the signal path by making the slot bigger, though at the same time making the PCN stub area smaller. By having such a design the PCN resonance frequency will be almost constant when making a GSM tuning.
According to a third aspect of the invention there is provided a method of adjusting the resonance frequency of at least two frequency bands of an antenna device comprising radiator elements integrated into a single radiator plate of a patch antenna being operable in at least two frequency bands and having adjustment parts that individually affects the frequency of said at least two bands in dependence of the size of these adjustment parts, said method comprises steps of individually adjusting the size of adjustment parts. Hereby the antenna design is prepared for long term variation of the transmitter stage. If the transmitter stage changes output characteristicsxe2x80x94e.g. due to the use of a new Power Amplifier from another vendor, the manufacturer is hereby provided with a method for matching the antenna device to these new characteristics instead of having to re-design the antenna due to the new components.
Furthermore the antenna is designed to have the highest voltage in the top of the phone in order to minimize coupling to the battery. The coupling between the end of the GSM part and the PCN stub is minimized in order to increase bandwidth of the antenna. The simple structure of the radiator gives the current a natural flow on the patch, which increases the bandwidth of the antenna.